With the development of technology, flat display panels (such as liquid crystal displays, organic light emitting diode displays and plasma displays etc.,) have been widely used in a variety of consumer electronics products (such as mobile phones, notebook computers, desktop displays and televisions etc.,) due to the features of high quality, small size, light weight and wide range of applications, etc. In addition, flat display panels also have gradually replaced the traditional cathode ray tube (CRT) display devices and become the mainstream of display devices.
Moreover, with being implemented with touch function, flat panel displays with touch function are further capable of providing a human-computer interaction interface, which make users have more intuitive experiences.
Today's light sensing touch panel usually employ a light sensing circuit to detect whether there is a touch object (for example, a light pen or finger) or not. Specifically, the light sensing circuit is configured to detect a touch event by the degree of leakage current, which is generated and corresponding to the illumination thereon; wherein a working window, resulted by the degree of the leakage current and related to the material characteristics of amorphous silicon, is an important factor for the determination of a touch event.
However, if having a too small working window, a light sensing circuit may be too much sensitive to a variety of environmental factors (such as voltage or temperature) and accordingly may generate a wrong determination about whether there has a touch event or not.